PSA incorporates a material called molecular sieve for gas separation. This zeolite based sieve has a preferential adsorption for nitrogen. Clean dry air is passed through the sieve beds on the oxygen generator, producing an oxygen enriched gas.

PSA oxygen generators provide the best performance when the feed air has a dew point of 40 degrees F & (4 degrees C) or less. Depending on the model selected and or the feed air equipment (air compressor, dryer, air surge tank and feed air filters) supplied, humidity control may or may not be required for the room. Consult factory for recommendations on a specific applications.

PSA oxygen generators have internal filters that have recommended element replacement about every 6 months under 24/7 operation. Additionally, valves will have to be rebuilt every few years. The majority of the maintenance will involve the service of the air compressor recommended by the air compressor manufacturer.

The molecular sieve life is based on the feed air quality. If the feed air quality always meets recommended standards, the sieve can last indefinitely (20 years or more!) If the molecular sieve ever became contaminated by oil, dirt or water can it be cleaned or replaced? If the molecular sieve is contaminated by oil it will have to be replaced. Water contamination, based on degree, does not necessarily mean that the sieve will need to be replaced. Dirt is a rare cause of sieve replacement, but other contaminates like ammonia can cause sieve failure. Consult factory for specific air contamination that may be present at the generator site.

Can the oxygen generator be operated with contaminated sieve, and what are the consequences?

A PSA oxygen generator may still operate after it has been contaminated, but a reduction in oxygen purity and flow should be expected. This may be critical in many applications, such as hospitals where the oxygen is being inhaled.

We would recommend only good quality feed air equipment (air compressor, dryer & feed air filter set) that can meet our air quality requirement of ISO 8573.1 class 1.4.1. The details of this specification are shown on our general arrangement drawing for each model. We also recommend using a good quality feed air equipment so the feed air is as good into the future as it was on day one.

The feed air quality specification for OGSI PSA oxygen generators requires a dew point value of 40 degrees F(4 degrees C) or less. If the local ambient air conditions are above this value, an air dryer will be required.

Can I use a dessicant dryer if I want, and are there any advantages or disadvantages?

A desiccant dryer can be used in place of a refrigerated dryer, and slightly better performance from the oxygen generator can be expected. However, this increase in performance may not offset energy and cost penalties.

The delivery pressure of oxygen from a PSA oxygen generator can usually be increased to the high end of the scale by decreasing the flow from the plant. Higher pressures would require an oxygen booster or compressor.

Some local authorities require 99% purity oxygen due to old regulations and ordinances. However, with the acceptance of international specifications from CSA (Canada) and ISO 10083 (European) these older specifications are being revised to 93%.

What is the difference between an oxygen concentrator and an oxygen generator?

These terms have been used interchangeably, with oxygen concentrator being the most technically accurate. Generically, oxygen concentrators describe smaller home medical systems, and oxygen generators describe all other size plants.

If millions of people, world-wide, use oxygen concentrators that produce 93% oxygen on a daily basis, why do some countries still specify 99% oxygen hospital supply systems?

There have been powerful competitive interests that have lobbied local authorities to maintain a 99% medical oxygen purity standard to prevent the introduction of less expensive alternatives like PSA oxygen generators.

Liquid oxygen has losses where a certain amount is lost to evaporation. Does PSA gaseous oxygen have the same problem?

It is normal for a LOX storage tank to bleed off 1 to 4% of the tank volume to prevent pressure built-up. This is not a factor with PSA oxygen generators, all the oxygen that is produced can be used, there is no bleed off.

Ideally, the hospital would design specifications or historical data to determine the plant size required. If this information is not available a formula can be used to estimate the peak oxygen required. Refer to the OGSI Hospital Application Note for details.

Are there concerns about carbon monoxide and carbob dioxide when producing gaseous oxygenusing PSA technology?

Most specifications for medical or breathable oxygen have maximum levels of carbon monoxide and carbon dioxide. It is important that the oxygen system has access to clean fresh air, and that a carbon monoxide and carbon dioxide monitor be used for medical or breathable applications.

It is possible that an oxygen (or any other type of gas cylinder) can become contaminated due to misuse. For this reason OGSI offers vacuum pumps on most CFP Models so that cylinders can be evacuated before they are filled.

It is never a bad idea to use a vacuum pump to empty a cylinder before it is refilled, especially if the cylinder is out of the control of the filler. This vacuum procedure can be eliminated if the cylinder is always in control of the filler.

Why do several models of cylinder plants cost almost the same, but produce very different amounts of oxygen?

On smaller CFP’s, the price does not change proportionately with plant size because of the standard equipment and instrumentation included with each skid. Also, there are only three standard sizes of oxygen compressors.

It is generally accepted that a 10 to 1 ratio of cylinders is required based on the output of the plant. For example, if a CFP-500 produces (50) cylinders per day, then (500) cylinders may be required to service the market. This ratio may change if the customer supplies the cylinder.

What equipment do I need to transfill a small cylinder from a large cylinder?

A high pressure flexible hose with an on/off valve and the corresponding cylinder valve connections at each end would be required. For safety, a containment vessel or chamber for the cylinder being filled is also recommended.

For PSA oxygen generators, the cost for oxygen production, or cylinder filling is normally stated in kilowatt hours (KWH). The reason being that the air is free, but there is a cost of electricity to operate the air compressor. At a sea level site elevation, it will cost about 10 KWH to fill a 6m3 size oxygen cylinder, or 1.5 KWH per M3.